Unlocking the potential of one-carbon gases (CO2, CO) for concomitant bioproduction of ß-carotene and lipids.

This study investigates the use of a Yarrowia lipolytica strain for the bioconversion of syngas-derived acetic acid into ß-carotene and lipids. A two-stage process was employed, starting with the acetogenic fermentation of syngas by Clostridium aceticum, metabolising CO, CO2, H2, to produce acetic acid, which is then utilized by Y. lipolytica for simultaneous lipid and ß-carotene synthesis. The research demonstrates that acetic acid concentration plays a pivotal role in modulating lipid profiles and enhancing ß-carotene production, with increased acetic acid consumption leading to higher yields of these compounds. This approach showcases the potential of using one-carbon gases as substrates in bioprocesses for generating valuable bioproducts, providing a sustainable and cost-effective alternative to more conventional feedstocks and substrates, such as sugars.

Inflow Artery Aneurysmal Degeneration After Long Term Native Arteriovenous Fistula for Haemodialysis.

OBJECTIVE: Inflow arterial aneurysms are a rare but serious complication after long term arteriovenous fistulae (AVF), probably due to arterial wall remodelling after an increase in flow and shear stress, and kidney transplantation with immunosuppressive therapy. This study aimed to describe the outcomes of surgical treatment and long term follow up in a large cohort. METHODS: This prospective cohort study collected data from patients with a true inflow artery aneurysm after AVF creation that was surgically repaired between 2010 and 2022. Anastomotic and infected aneurysms or post-puncture pseudoaneurysms were excluded. Demographic data, access characteristics, symptoms, treatment strategies, and long term follow up were recorded; patency was estimated using Kaplan-Meier survival analysis. RESULTS: During the study period, 28 patients (64% men, mean age 60.1 years) were treated surgically for aneurysmal degeneration of the axillary or brachial (n = 23) or radial (n = 5) artery after an AVF (10 distal, 18 proximal) performed a mean of 18.3 ± SD 7.9 years previously. Most AVFs were ligated or thrombosed, while all patients except one had previously received kidney transplants. Most of the cases (n = 18) were symptomatic: 13 with pain or swelling, four with distal embolisation, and one rupture. They were repaired by aneurysm partial excision and graft interposition (11 great saphenous vein, six ipsilateral basilic vein, three cephalic vein, and two PTFE graft), ligation (n = 3), or direct end to end anastomosis (n = 3). No major complications occurred before discharge, after a mean hospital stay of 2.4 days. After a mean follow up of 4.8 ± 3.3 years, three cases presented complications: two recurrent proximal brachial aneurysms were repaired with an additional proximal interposition graft (one with further late infected pseudoaneurysm) and an asymptomatic post-traumatic graft thrombosis. Five year primary and secondary patency was 84% and 96%, respectively. CONCLUSION: Aneurysmal degeneration of the inflow artery is an unusual complication during long term follow up of AVFs. Aneurysm excision and, in general, autogenous graft interposition using the saphenous or ipsilateral arm vein is a safe and effective strategy.

Impact of Target Visceral Vessel Anatomical Configuration on Early Complications Following Endovascular Repair of Thoracoabdominal Aortic Aneurysms.

BACKGROUND: Fenestrated and branched endovascular aortic repair (fEVAR-bEVAR) is a viable treatment option for thoracoabdominal aortic aneurysms but target visceral stent (TVS) endoleak and thrombosis remain a limiting factor. This study aims to evaluate TVS anatomy impact on 1-year risk of thrombosis and endoleak. METHODS: Patients treated with fEVAR-bEVAR for thoracoabdominal aneurysms between 2008 and 2020 in our centre were enrolled. We recorded comorbidities, operative details, 1-month postoperative CT scan (anatomical reference), and TVS behaviour: thrombosis and endoleak at 1-year follow-up. For each TVS, different points were identified using a centre-lumen-line: (A) TVS origin, (B) end of branch/fenestration, (C) visceral vessel entry, (D) end of TVS, (E) 1-cm distally. We analyzed TVS tortuosity ((centre-lumen-line/straight distance)-1, in %), image vector analysis of each segment in 2D (antero-posterior, left-right) and 3D (craneo-caudal displacement), and centre-lumen-line analysis (bending in ABC and CDE). Three independent observers performed a blind analysis, and anatomical differences between bEVAR/fEVAR, and cases with/without 1-year thrombosis and TVS endoleak, were compared using Kaplan-Meier curves (Log-Rank test), and t-test/Wilcoxon signed-ranks test respectively. RESULTS: Fifty-four patients (72 ± 713 years mean age; 182 TVS: 50 branches, 132 fenestrations) met the inclusion criteria. bEVAR cases had longer stents, with more caudal 3D angulation, and greater ABC angulated segment. After excluding bEVAR cases (low case number), 97 fEVAR TVS were analyzed. Five thrombosis and 7 endoleaks were observed. While anatomical configuration showed no association to thrombosis, it was related to endoleak: these cases presented more tortuous stents (5.97% ± 0.10, 21.40% ± 0,22, P = 0.011), with more angulated centre-lumen-line at ABC segment (5.69° ± 15.77°, 7.18° ± 7.77°, P = 0.012), and more upward-pointing stents in the origin of the stent (AB: 89.07° ± 24.46°, 109.09° ± 16.56°, P = 0.012; BC: 87.86° ± 21.10°, 113.11° ± 22.23°, P = 0.026). CONCLUSIONS: Anatomical configuration of the TVS is associated with type III endoleak, but not thrombosis, at 1-year following fEVAR. Cases with endoleak presented more tortuous stents, with a more angulated exit from the endograft, and upward-pointing of the origin of the stent.

Efficient production of n-caproate from syngas by a co-culture of Clostridium aceticum and Clostridium kluyveri.

In recent years, the possibility of merging technologies for waste recovery such as those based on syngas fermentation and chain elongation has been studied for the production of medium chain fatty acids (MCFAs) and bioalcohols, in an attempt to integrate the concept of circular economy in the industry. Nevertheless, one of the main issues of this approach is the pH mismatch between acetogens and chain elongating microorganisms. This work reports, for the first time, the suitability of a co-culture of C. aceticum and C. kluyveri metabolizing syngas at near neutral pH in stirred tank bioreactors. For this purpose, bioreactor studies were carried out with continuous syngas supply. In the first experiment, maximum concentrations of n-butyrate and n-caproate of 7.0 and 8.2 g/L, respectively, were obtained. In the second experiment, considerable amounts of n-butanol were produced as a result of the reduction, by C. aceticum, of the carboxylates already formed in the broth. In both experiments, ethanol was used as an exogenous electron agent at some point. Finally, batch bottle assays were performed with a pure culture of C. aceticum grown on CO in presence of n-butyrate to assess and confirm its ability to produce n-butanol, reaching concentrations up to 951 mg/L, with a n-butyrate conversion efficiency of 96%, which had never been reported before in this species. Therefore, this work contributes to the state of the art, presenting a novel system for the bioproduction of MCFAs by combining syngas fermentation and chain elongation at near neutral pH, as opposed to the acidic pH range used in all previously reported literature.

Prospective Multicenter Study of the Low-Profile Relay Stent-Graft in Patients with Thoracic Aortic Disease: The Regeneration Study.

BACKGROUND: To evaluate the early safety and clinical performance of the new low-profile RelayPro Thoracic Stent-Graft System in patients with thoracic aortic disease. METHODS: This was an international, prospective, single-arm study in patients diagnosed with thoracic aorta disease (aneurysm, pseudoaneurysm, dissection, penetrating atherosclerotic ulcer, or intramural hematoma) and treated with a RelayPro stent-graft (in bare stent and/or nonbare stent configurations). The primary endpoints were freedom from aneurysm or dissection-related mortality and stent-graft performance. RESULTS: A total of 31 patients were treated with the RelayPro thoracic stent-graft between 2014 and 2015 at 8 sites in Italy and Spain. Mean age was 72.1 (±10.2) years and 77% were male, 74% with hypertension, and 42% with a history of smoking. Twenty-four (77%) had aneurysms (fusiform in 46%, saccular in 42%, pseudoaneurysm in 12%); 5 (16%) had penetrating atherosclerotic ulcer; and 2 (6%) had chronic Type B dissection. Mean vascular access diameter was 9.1 mm (6-13 mm); 7 patients (23%) had vascular access of 7 mm or less. Technical success was 100% (primary, 90%; assisted primary, 10%). Freedom from aneurysm/dissection-related mortality through 30 days was 100%. Freedom from device-related major adverse events through 30 days was 94%. At 1 year, there was 1 (3%) type Ib and 1 (3%) type II endoleak, 1 (3%) nonaneurysm-related late death, and 1 (3%) secondary intervention (to correct type Ib endoleak). CONCLUSIONS: The RelayPro has a 3-4 French profile reduction to allow endovascular repair of thoracic aortic disease in patients with smaller anatomies. This study shows good initial stent-graft performance and a favorable early safety profile.

Aortic Curvature Remodeling after Thoracic Endovascular Aortic Repair: Assessing Device Conformability, Using Image Vector Analysis.

BACKGROUND: Aortic arch curvature can be straightened by endograft placement. However, different measurement methods with dissimilar follow-up and endografts have been published. The aim of this study was to corroborate, for the first time, the pliability of the Conformable Gore TAG Thoracic Endoprosthesis (W.L. Gore and Associates, Flagstaff, AZ, USA) into the aortic arch, using different image vector analysis. MATERIAL AND METHODS: We, retrospectively, analyzed patients primarily treated for thoracic aortic aneurysms and blunt traumatic aortic injuries by means of a Conformable Gore TAG Thoracic Endoprosthesis endograft proximally sealed into the aortic arch (zones Z1-Z3) in five different Spanish centers, between 2010 and 2017. The preoperative, one-month and six-month postoperative, computed tomography angiographies (CTAs) were obtained, creating accurate 3D center lumen line and external lumen line from the aortic valve to the renal arteries. Three different image analysis methods were used to compare modifications of the aortic curvature: first, segment analysis (angulations of the center lumen line when divided into seven precise segments, examining anterior-posterior, right-left, and cranial-caudal displacement), second, center lumen line analysis (bending of the center lumen line itself in seven definite points), and third, expected behavior (length of the endograft in the external lumen line). Two independent observers performed a blind analysis of all CTAs. Changes between preoperative and postoperative CTAs at one and six months are compared, and differences are viewed between cases sealed proximally (Z1-Z2) and distally (Z3) into the aortic arch. RESULTS: We analyzed 37 cases. At 1- and 6-month follow-ups, minimal changes occurred first in segment analysis (only a slight decrease of -2.0° in the XY plane at 10 cm from the brachiocephalic trunk at six-month follow-up was seen, P = 0.027). Second, center lumen line analysis again only showed negligible aortic curvature straightening (+3.5° at 10 cm from the brachiocephalic trunk at one month, P = 0.006, disappearing at six-month follow-up). Finally, good device length predictability was shown (interclass correlation coefficients: 0.995 and 0.994 at one and six months, P > 0.001). No differences were seen between cases proximally sealed into the proximal and distal aortic arch. CONCLUSIONS: Conformable Gore TAG Thoracic Endoprosthesis thoracic endograft showed a good pliability into the aortic arch and proximal thoracic aorta, with minimal changes in the aortic curvature after endograft placement in the short-term follow-up (up to six months). In addition, final endograft length into outer aortic curvature is highly predictable.

Carbon dioxide as key player in chain elongation and growth of Clostridium kluyveri: Insights from batch and bioreactor studies.

Chain elongation technology allows medium-chain fatty acids (MCFAs) production as an alternative to fossil resources. Clostridium kluyveri generates n-caproate primarily from ethanol and acetate, presumably requiring CO2 for growth. Here, the impact of CO2 on C. kluyveri was explored. Bottle studies revealed the bacterium's adaptability to low CO2 levels, even in conditions with minimal dissolved NaHCO3 (0.0003 M) and unfavorable pH (below 6) under 1 bar CO2. Bioreactor investigations demonstrated a direct correlation between CO2 availability and bacterial growth. The highest n-caproate production (11.0 g/L) with 90.1 % selectivity was achieved in a bioreactor with continuous CO2 supply at 3 mL/min. Additional bottle experiments pressurized with 1 bar CO2 and varying ethanol:acetate ratios (1:1, 2:1, 4:1) also confirmed CO2 consumption by C. kluyveri. However, increasing the ethanol:acetate ratio did not enhance n-caproate selectivity, likely due to overly acidic pH conditions. These findings provide insights into chain-elongators responses under diverse conditions.

Comprehensive comparative study on n-caproate production by Clostridium kluyveri: batch vs. continuous operation modes.

Recently, there has been notable interest in researching and industrially producing medium-chain carboxylic acids (MCCAs) like n-caproate and n-caprylate via chain elongation process. This study presents a comprehensive assessment of the behavior and MCCA production profiles of Clostridium kluyveri in batch and continuous modes, at different ethanol:acetate molar ratios (1.5:1, 3.5:1 and 5.5:1). The highest n-caproate concentration, 12.9 ±â€¯0.67 g/L (92.9 ±â€¯1.39 % MCCA selectivity), was achieved in batch mode at a 3.5:1 ratio. Interestingly, higher ratios favored batch mode selectivity over continuous mode when this was equal or higher to 3.5:1. Steady state operation yielded the highest n-caproate (9.5 ±â€¯0.13 g/L) and n-caprylate (0.35 ±â€¯0.020 g/L) concentrations at the 3.5:1 ratio. Increased ethanol:acetate ratios led to a higher excessive ethanol oxidation (EEO) in both operational modes, potentially limiting n-caproate production and selectivity, especially at the 5.5:1 ratio. Overall, this study reports the efficient MCCA production of both batch and continuous modes by C. kluyveri.

Effect of electron acceptors on product selectivity and carbon flux in carbon chain elongation with Megasphaera hexanoica.

Megasphaera hexanoica is a bacterial strain following the reverse ß-oxidation pathway to synthesize caproate (CA) using lactate (LA) as an electron donor (ED) and acetate (AA) or butyrate (BA) as electron acceptors (EA). Differences in the type and concentration of EA lead to distinctions in product distribution and energy bifurcation of carbon fluxes in ED pathways, thereby affecting CA production. In this study, the effect of various ratios of AA, BA, and AA+BA as EA on carbon flux and CA specific titer during the carbon chain elongation in M. hexanoica was explored. The results indicated that the maximum levels of CA were 18.81 mM and 31.48 mM when the molar ratios of LA/AA and LA/BA were 10:1 and 3:1, respectively. Meanwhile, when AA and BA were used as combined EA (LA, AA, and BA molar amounts of 100, 23, and 77 mM), a maximum CA production of 39.45 mM was obtained. Further analysis revealed that the combined EA exhibited a CA production carbon flux of 49 % (4.3 % and 19.5 % higher compared to AA or BA, respectively) and a CA production specific titer of 45.24 mol (80.89 % and 58.51 % higher compared to AA or BA, respectively), indicating that the effective carbon utilization rate and CA production efficiency were greatly improved. Finally, a scaled-up experiment was conducted in a 1.2 L (working volume) automated bioreactor, implying high biomass (optical density at 600 nm or OD600 = 1.809) and a slight decrease in CA production (28.45 mM). A decrease in H2 production (4.11 g/m3) and an increase in CO2 production (0.632 g/m3) demonstrated the appropriate metabolic adaptation of M. hexanoica to environmental changes such as stirring shear.

Autologous forearm arteriovenous loop vascular access, an option to be considered.

BACKGROUND: Autologous arteriovenous fistula is usually the vascular access of choice for hemodialysis in patients with chronic kidney disease. Autologous forearm loops with cephalic or basilic vein are an alternative in those cases with a suitable forearm vein but with an unsuitable radial artery; however they are rarely used and there is little reported evidence of their usefulness. Our objective is to report our results on the creation of autogenous forearm loops as vascular access for hemodialysis. METHODS: We present a prospective cohort study of autogenous forearm loop arteriovenous fistula created between 2010 and 2022, in patients with stage 4-5 chronic kidney disease. Demographic data, surgical details, vein used, follow up to 24 months, maturation, utilization, primary, assisted, and secondary patency estimations with Kaplan-Meier curves, as well as complications during follow-up, were recorded. RESULTS: During the study period, 22 autologous forearm loops were created, 14 of them with cephalic, and 8 with basilic vein. Most (59%) of the patients were men, 19 were already on dialysis and the rest started during follow-up. Sixteen patients had previous vascular accesses. One patient was lost during follow-up. Six-week maturation rate was 61.9% and utilization rate was 57.1%. 6, 12, and 24 months primary and secondary patencies were 75.4%, 59.2%, 41.5% and 85.0%, 69.5%, 56.9% respectively. In five patients an access-induced distal ischemia was diagnosed, four successfully treated and only one patient lost the access. No cases of infection or other major complications were reported. CONCLUSION: Autologous forearm loops have acceptable maturation (61.9%) and patency rates at follow-up (56.9% 2-years secondary patency). Although rarely used, they are a vascular access alternative that should be considered to preserve the proximal vasculature of the arm for future accesses.

Effect of pH and medium composition on chain elongation with Megasphaera hexanoica producing C4-C8 fatty acids.

Introduction: Chain elongation technology, which involves fermentation with anaerobic bacteria, has gained attention for converting short and medium chain substrates into valuable and longer-chain products like medium chain fatty acids (MCFAs). In the recent past, the focus of studies with pure chain elongating cultures was on species of other genera, mainly Clostridium kluyveri. Recently, other chain elongators have been isolated that deserve further research, such as Megasphaera hexanoica. Methods: In this study, batch studies were performed in bottles with two different media to establish the optimal conditions for growth of M. hexanoica: (a) a medium rich in different sources of nitrogen and (b) a medium whose only source of nitrogen is yeast extract. Also, batch bioreactor studies at pH values of 5.8, 6.5 and 7.2 were set up to study the fermentation of lactate (i.e., electron donor) and acetate (i.e., electron acceptor) by M. hexanoica. Results and discussion: Batch bottle studies revealed the yeast extract (YE) containing medium as the most promising in terms of production/cost ratio, producing n-caproate rapidly up to 2.62 ± 0.24 g/L. Subsequent bioreactor experiments at pH 5.8, 6.5, and 7.2 confirmed consistent production profiles, yielding C4-C8 fatty acids. A fourth bioreactor experiment at pH 6.5 and doubling both lactate and acetate concentrations enhanced MCFA production, resulting in 3.7 g/L n-caproate and 1.5 g/L n-caprylate. H2 and CO2 production was observed in all fermentations, being especially high under the increased substrate conditions. Overall, this study provides insights into M. hexanoica's behavior in lactate-based chain elongation and highlights optimization potential for improved productivity.

Production of biofuels from C1 -gases with Clostridium and related bacteria-Recent advances.

Clostridium spp. are suitable for the bioconversion of C1 -gases (e.g., CO2 , CO and syngas) into different bioproducts. These products can be used as biofuels and are reviewed here, focusing on ethanol, butanol and hexanol, mainly. The production of higher alcohols (e.g., butanol and hexanol) has hardly been reviewed. Parameters affecting the optimization of the bioconversion process and bioreactor performance are addressed as well as the pathways involved in these bioconversions. New aspects, such as mixotrophy and sugar versus gas fermentation, are also reviewed. In addition, Clostridia can also produce higher alcohols from the integration of the Wood-Ljungdahl pathway and the reverse ß-oxidation pathway, which has also not yet been comprehensively reviewed. In the latter process, the acetogen uses the reducing power of CO/syngas to reduce C4 or C6 fatty acids, previously produced by a chain elongating microorganism (commonly Clostridium kluyveri), into the corresponding bioalcohol.